Combinations of position information and content information with various geographical information have been developed. The geographical information is utilized in various fields such as disaster prevention, security and traffic by using mobile communication techniques. The utilization of geographical information is called Location Based Services (LBSs). In the LBS, services and contents suitable for the position and environment of users are provided.
Infrastructure necessary to implement the LBS and main technical objects may include high-accuracy three-dimensional spatial data as well as a seamless positioning system, a communication system, a terminal and display technique and others that enable the position to be obtained in a wide range of space including indoors and outdoors.
As one example, the seamless positioning system includes wireless LAN based positioning.
Currently, services for positioning based on reception of radio waves transmitted from wireless LAN access points located in personal residences, business offices, cafes, train stations and so on are commonly available. Enormous numbers of wireless LAN access points are located in train stations and business areas. Wireless LAN based positioning services are extremely effective as positioning methods for train stations and business areas. Particularly, in using the Global Positioning System (GPS), the wireless LAN based positioning services are advantageous in an underground area where radio waves cannot be properly received from GPS satellites.
A positioning apparatus incorporated in a mobile communication terminal uses wireless LAN to perform positioning by detecting (finding) beacon signals transmitted from a neighboring access point and measuring the distance to the access point based on received strength of the beacon signals. See JP 2009-543074, for example.